1. Field of the Invention
The present invention is broadly concerned with security assemblies adapted for connection to doors or similar movable objects, in order to provide an alarm function in the event of unauthorized opening of the doors. More particularly, it is concerned with such security assemblies, as well as switch assemblies forming a part thereof wherein the security assemblies have one or more switch assemblies each having a magnetically operated switch member.
2. Description of the Prior Art
Prior art security alarm systems often make use of magnetic switches attached to doors and windows which are integrated within a system for detecting unauthorized openings. One common type of magnetic switch used in these situations is a so-called reed switch. Reed switches are subject to unauthorized manipulation through use of an external magnet, allowing an intruder to open a door or window without triggering the alarm system.
A number of magnetic switches have been proposed in the past to overcome deficiencies of reed switches. U.S. Pat. Nos. 5,977,873, 5,530,428, 5,332,992, 5,673,021, and 6,603,378 describe switches having a pair of spaced apart switch elements with a shiftable body (e.g., a spherical ball) movable between a first position where the ball is in simultaneous contact with both switch elements, and a second position out of such simultaneous contact. An alarm circuit is operatively coupled with the switch element so as to detect movement of the body and a corresponding change in electrical state of the switch element, which in turn triggers an alarm function.
Cargo containers which are moved or shipped over long distances present a significant security problem. For example, unless properly protected, such containers may be opened en route and the contents thereof stolen. Also, such containers could be opened and a bomb or other terrorist device inserted therein. Accordingly, it is very important that such containers be secured against unauthorized access. One problem in this regard is that most prior security systems require a source of AC power, which is not feasible when seeking to protect shipping containers.